We found a new species of the
genus Hemigastrostyla Song & Wilbert, 1997 in sandy
sediments of the Jiaozhou Bay (Yellow Sea, China). Species of
this marine/brackish genus have, like many other hypotrichs,
basically an 18 frontal-ventral-transverse cirri pattern. Previously,
all 18-cirri hypotrichs have been assigned to the oxytrichids
because the characteristic pattern formed by the 18 cirri was
interpreted as apomorphy of this group (Kahl 1932, Tierwelt Dtl.
25; Berger 1999, Monographiae biol. 78). Interestingly, the classification
based on the ventral ciliature is in conflict with the dorsal
kinety pattern and most gene sequence data, indicating that this
complex 18-cirri pattern must have evolved much earlier in the
Hypotricha tree, very likely already in their stemline (Berger
2008, MB 85). Due to these changes in hypotrich taxonomy, some
genera - for example, Oxytricha and Hemigastrostyla
- are obviously no longer monophyletic. Oxytricha granulifera
Foissner & Adam, 1983 - type of the notoriously difficult
genus Oxytricha Bory de Saint-Vincent, 1824 - has a dorsal
kinety 3 fragmentation and dorsomarginal kineties. Consequently,
Oxytricha species which lack the fragmentation (e.g.,
Oxytricha islandica Berger & Foissner, 1989; O.
lanceolata Shibuya, 1930; O. longa Gelei & Szabados,
1950) have to be transferred to a (new?) genus outside the oxytrichids,
but within the Dorsomarginalia Berger, 2006 which unify all hypotrichs
having a dorsomarginal kinety. By contrast, Oxytricha species
which lack both kinety fragmentation and dorsomarginal rows [e.g.,
Oxytricha geleii (Wilbert, 1986)] have to be placed outside
the Dorsomarginalia, that is, near the base of the Hypotricha
tree.
Funded by the National Natural Science Foundation of China (Project
40906065; C. Shao, W. Song) and the Austrian Science Fund (FWF;
Project P23415-B17; H. Berger).